SN Certified Technician

Thank you sir. I test my voltages at the EFI panel I have so I use a cross-reference to find the right spots to test. That is helpful for testing the computer pins though.

So, there is definitely a problem with the ACT. I am not getting any voltage across the sensor pins. When I check the ECT voltage, I get 3.5V, which is right on par for around 50 degrees. I checked the resistance on the ACT sensor without it hooked up and the numbers checked out. About 55k ohms in the garage and the resistance kept dropping when I brought the sensor in the house. So, it appears there is a wiring problem. I'm going to bypass the PMS to make sure there is nothing in that box of magic messing things up and then go from there. I checked the computer itself when disconnected and got 18.6k ohms for both the ACT and ECT sensors with pin 46 as a ground reference. I 'think' that tells me that the computer itself is okay.

So I was re-checking all the tables in the PMS. For some reason I had +18 in the water temp table at -10 degrees. I remember troubleshooting a cold running issue with my old setup and that may be how I was trying to solve it. That +18 was adding a ton of fuel with the engine cold. Explains why everything was flooding out.

The other problem I noticed is that the PMS is displaying -30 degrees for the air temp sensor. I pulled off the plug and installed another new (auto parts store) sensor. Still read -30 degrees. I shot it with the heat gun and it still didn't changed. I held the heat gun to the water temp sensor and it went from 54 degrees to 60 degrees in seconds. I obviously have some issues I have to figure out. Not sure why it doesn't work with two brand new sensors. That makes me a bit concerned. Time to do some EEC troubleshooting.

Click to expand...

How do you like the PMS? I've contemplated using it myself. If starting from scratch would you use it again or go with a standalone?

SN Certified Technician

How do you like the PMS? I've contemplated using it myself. If starting from scratch would you use it again or go with a standalone?

Click to expand...

I like it a lot. If I were to do it all over again and money or time wasn't an issue, I would probably go with a standalone system. I like the idea of adding modern features like coil packs and cam sensors to these engines. Allows for more tuning capabilities, but can create more problems due to added complexity. I already have a somewhat decent grasp on the PMS, so I didn't feel like learning a brand new system. A PMS can be had used on the classifieds for around $500 these days. They have come down in price a good bit over the past few years.

Founding Member

Sorry for the constant questions, but you are doing a few of the same things I'm trying to do....

Anyways, did you by any chance figure out how to wire up the low fuel light and Check Engine light? The pinouts don't specify the CE light feed for 87-89 even though my stock cluster has one. And the low fuel has a pin out for the relay and the warning, do you know if i have to somehow utilize both or just one?

Again, sorry for the questions. Im sure I will have more. Florida 5.0 and MC Machine aren't very forthcoming with wiring information, not that i blame them.

SN Certified Technician

I'll have to check my diagram later tomorrow and let you know which pin I used for the CEL. My aftermarket EFI wiring is based off 91 factory wiring, so it may be different. I can't help you with the low fuel light though. I don't have one. I didn't really find it necessary to have a light when I can just keep an eye on the gauge. I'll never allow my sumped tank to get low enough to activate a light anyway.

Afaik the sd carz dont have a functional engine light, the bulbs there but nothing to turn it on, so I wouldn't be surprised if it wasn't in the 87/88 diagram, but I can try to find it in my 89 diagram when I get home. ...if I can remember to do it

Admin Dude

So I was re-checking all the tables in the PMS. For some reason I had +18 in the water temp table at -10 degrees. I remember troubleshooting a cold running issue with my old setup and that may be how I was trying to solve it. That +18 was adding a ton of fuel with the engine cold. Explains why everything was flooding out.

The other problem I noticed is that the PMS is displaying -30 degrees for the air temp sensor. I pulled off the plug and installed another new (auto parts store) sensor. Still read -30 degrees. I shot it with the heat gun and it still didn't changed. I held the heat gun to the water temp sensor and it went from 54 degrees to 60 degrees in seconds. I obviously have some issues I have to figure out. Not sure why it doesn't work with two brand new sensors. That makes me a bit concerned. Time to do some EEC troubleshooting.

Click to expand...

I don't think it's your EEc man. I think you have a harness/wiring problem someplace and getting either stray voltage or grounding out.

Edit: Meh... I hate it when I walk into a thread and read what appears to be the last post, only to discover that there's another dozen after.